Sex offender's deviant fantasies have 'ruined his life', court told

Prosecutors say a self-confessed sexual deviant who indecently assaulted a woman in an opportunistic attack in Adelaide's north should be given a significant jail sentence to protect other members of the public.

The court heard Dyer handed himself into police three days after sexually assaulting a young woman near a bus stop at Mawson Lakes on Boxing Day last year.

Dyer approached the woman from behind, threatened her with a knife and told her to get down before he sexually assaulted her and stole her iPod.

He later told police he discarded the iPod and did not know why he took it.

Prosecutor Jill Lieschke said it was a random attack and argued a significant jail sentence was warranted to protect the community.

"The accused admitted an inability to control himself," he said.

"He made admissions to police that certainly are extremely concerning and show a very long-standing thought process that led up to the offence on the day in question.

"This was a very vulnerable victim, she was a stranger, she was a young female, a knife was used and she was approached from behind. There was quite significant trauma to her."

A victim impact statement was read to the court in which the woman said she lived in constant fear and no longer caught the same bus.

She also expressed concern that her attacker would find her when he is released.

"This particular offending calls for a significant custodial penalty. Of paramount consideration should be general deterrence and protection of the public," Ms Lieschke said.

'Time bomb'

Dyer told police he had been battling deviant thoughts about harming women all his life but had sought help before his offending.

His lawyer Julian Kelly says he accepts his client will go to jail but urged a lower-than-usual non-parole period.

Mr Kelly told the court his client had been battling paraphilia, or sexually deviant thoughts, all his life and said the case involved "considerable sadness".

"Sadness not only for the victim who in no way deserved to be molested and robbed by the accused and will no doubt continue to suffer psychological damage as a consequence, but also sadness for the accused who has been battling paraphilia for virtually all of his life," he said.

"It's brought him to the point of suicide on many number of occasions and brought him to seek help from mental health services."

The court heard Dyer had been admitted into numerous psychiatric facilities where he sought help for his sexual sadism.

"That was him trying to deal with his problem, realising he had a serious problem and had to do something about it," Mr Kelly said.

"He didn't need the shock of court proceedings to lead him into that treatment program or programs that he's been involved in.

"Certainly it's not a typical case. He's not a serial offender. With his paraphilia he could easily have been and it's been the battle of his life to fight these tendencies."

Judge Barry Beazley said it seemed odd that three independent psychiatrists found no evidence of any major psychotic disorder.

The court heard Dyer was assessed as having a borderline personality disorder, which is not consistent with a major psychotic diagnosis.

"A time bomb waiting for release unless there's some form of treatment," Judge Beazley said.

Mr Kelly said his client's rehabilitation would benefit from a longer period on supervised parole and his client had been undertaking chemical castration to address his deviant sexual thoughts.

"Mr Dyer is determined to engage with whatever agencies can assist him to overcome this problem; it's ruined his life really," he said.

The court heard Dyer had written a letter of apology.

"He expresses a clear understanding that his apology, his rehabilitation efforts, his medical castration and his imprisonment, and imprisonment in an ongoing sense, would at best just be a starting point for [the victim's] recovery.

"He stated that since his arrest and incarceration he's been recommenced on regular medication and has been able to reduce his preoccupation with unwanted thoughts, particularly because the memory of what he did upsets him, and as a result he's noticed an almost complete absence of libido and almost an aversion to fantasising about sex.

"We accept the seriousness of the offending and accept that imprisonment is the only appropriate penalty. In all of the unusual circumstances of this case, I submit a lower-than-usual non-parole period would be appropriate to be imposed.

"My client has instructed that he'd rather kill himself than reoffend."